import * as ts from 'typescript';

function walkToNodeWithJSDoc(node: ts.Node): (ts.Node & { jsDoc?: ts.Node[] }) | undefined {
  let relevantNode: (ts.Node & { jsDoc?: ts.Node[] }) | undefined = node;
  while (relevantNode) {
    const { jsDoc } = relevantNode;
    if (jsDoc && jsDoc instanceof Array && jsDoc.length > 0) {
      return relevantNode;
    }
    relevantNode = relevantNode.parent;
  }
  return relevantNode;
}

export function extractDocumentationText(decl: ts.Declaration): string | undefined {
  const n = walkToNodeWithJSDoc(decl);
  if (!n) {
    return undefined;
  }
  const { jsDoc }: { jsDoc?: ts.Node[] } = n;
  if (jsDoc && jsDoc.length > 0) {
    const commentText: string = jsDoc[0].getText();
    return commentText;
  }
  return undefined;
}